I am not trying to single out this post, but half the thread seems to be assuming Fermi's paradox is about alien civilisations communicating with us over radio. This is 100% wrong. We are all actually talking about a paradox that was never postulated.

First, it has to be pointed out that the radio-wave idea has been discounted many times for a much more obvious reason. The period of time that any civilisation engages in communication by radio waves is likely to be a tiny fraction of a percentage of the total life of said civilisation. The idea of finding our alien friends through listening to radio waves was ridiculous when Carl Sagan was promoting it and remains so today.

Secondly, The Fermi Paradox is about alien civilisations *colonising* the Galaxy or "arriving here." It was originally phrased as the question "where are they?" (i.e. - they should be here by now given a finite universe and a certain amount of time.) As flawed as *that* idea also is, it's a completely different flawed idea than what most folks her are arguing about, which is the incredibly super-duper flawed idea of radio communication between advanced civilisations.

The thing I find interesting about the whole debate, is that for as long as I can remember scientists have been vilifying Velikovsky for his theories about exactly this kind of thing, and now all of a sudden (like over the last five years or so), this kind of "Planets in Collision" theory has become the standard view.

Sure Velikovsky was a bit of a crackpot and the specifics of his theories are pretty much made-up, but he was the first person to take a look at the same evidence quoted in this article and evolve some reasonable suppositions from it. At the time, his idea that planets could actually move around and change orbits, colide with others etc. and *especially* the idea that stars outside of the solar system or other objects could significantly affect our own planets, was roundly ridiculed.

He noted the same time period, the same planetary anomalies and supposed almost the exact same cause, yet for decades and decades he was made out to be absolutely crazy for saying these things. Now we talk about the "late-early bombardment" as if it has always been the standard line, when you would be chucked out of your academic job for believing in this stuff only a short time ago.